WHAT IS TESTOSTERONE?

What is testosterone? Testosterone is the most important sex hormone or androgen produced in men. It is the hormone that is primarily responsible for producing the normal adult male characteristics. During puberty, testosterone stimulates the physical changes that constitute the attributes of the adult male.

These attributes or characteristics of the adult male include:

• enlargement of the testes and penis
• growth of facial and pubic hair
• deepening of the voice
• increase in muscle mass and strength
• growth in height

Purpose and Production of Testosterone in Adult Males

Testosterone helps maintain sex drive, the production of sperm cells, male hair patterns, muscle mass and bone mass throughout male adult life. Testosterone is produced by the male testes and adrenal cortex. Small amounts of testosterone are produced by the ovaries in females.

The pituitary and hypothalamus glands in the brain tell the testes how much testosterone to produce. The hypothalamus gland in the brain regulates hormone production in the pituitary gland by secretion of gonadotropin-releasing hormone (GnRH). Gonadotropin-releasing hormone stimulates the pituitary gland to produce follicle-stimulating hormone (FSH) and luteinizing hormone (LH, also known as lutropin). LH stimulates the testes to produce testosterone. If the testes are producing too much testosterone, the hypothalamus sends signals to the pituitary gland to produce and release less LH. The decrease in the production and release of LH cause the testes to reduce the production of testosterone. If the testes are not producing a sufficient volume of testosterone, the hypothalamus releases more GnRP and the pituitary gland responds by increasing production and release of more LH, which stimulates the testes to make more testosterone. As men age, the production of LH and testosterone declines. Both testosterone hormone replacement therapy and HCG therapy are used to increase testosterone in men with low testosterone.